Finding the radius of a brass ball using tension?

[rought]

Homework Statement

One end of a wire is attached to a ceiling and a solid brass ball is tied to the lower end. The tension in the wire is 120N what is the radius of the brass ball.

Homework Equations

Brass Mass Density (kg/m^3) = 80470


I have no clue how to solve this one, can anyone help?

 

[hage567]

Start by drawing a free body diagram. You need to figure out the mass of the ball. How do you think you might do that?

 

[rought]

Start by drawing a free body diagram. You need to figure out the mass of the ball. How do you think you might do that?

Could you find the mass of the ball by taking the tension and dividing it by the force of gravity? Would tension equal the weight force (Mass x Gravity) ?

 

[Doc Al]

Could you find the mass of the ball by taking the tension and dividing it by the force of gravity? Would tension equal the weight force (Mass x Gravity) ?

That's correct. Two forces act on the ball: The upward tension of the wire and the downward pull of gravity. They must balance, thus: T = mg.

 

[rought]

That's correct. Two forces act on the ball: The upward tension of the wire and the downward pull of gravity. They must balance, thus: T = mg.

Ok I got that, but how do you find the radius of the ball from the volume that I calculated from the mass?

 

[hage567]

What's the formula for the volume of a sphere?

 

[rought]

What's the formula for the volume of a sphere?

V = (4/3)πR^3 right?

 

[hage567]

That's right.

 

[rought]

That's right.

Alrite I get what to do now, thanks a ton =]

 

[hage567]

You're welcome.